How do i plot two graphs in the same figure without it telling me that the vectors must be the same length?

Sorry for inputting my entire code but i am new to matlab.

I am trying to get two Voltages (Spanning & Spanning_fit) into the same graph with time (Tijd) on the x axis.

But it won't let me and gives me the error: 'vectors must be the same length'. I know they are not but i am totally new to this.

Any ideas? Sorry if my question is really unclear.

 load ("coltdata_busdaq_personalised.mat")

Error using load
Unable to find file or directory 'coltdata_busdaq_personalised.mat'.

        A = data;
         
        Tijd = A (2:21838,1);
        Spanning = A (2:21838,2);
        Stroom = A (2:21838,3);
        Snelheid_ms = A (2:21838,4);
        Snelheid_kmh = A (2:21838,5);
        Kracht = A (2:21838,6);
        Efficientie = A (2:21838,7);

        figure;
        subplot(3,2,1);
        plot(Tijd,Spanning,'r'); hold on
        xlabel('Tijd(s)')
        ylabel('Spanning(V)')
        grid;

        subplot(3,2,2);
        plot(Tijd, Stroom,'g'); hold on
        xlabel('Tijd(s)')
        ylabel('Stroom(A)')
        grid;
        
        subplot(3,2,3);
        plot(Tijd,Snelheid_ms,'b'); hold on
        xlabel('Tijd(s)')
        ylabel('Snelheid(m/s)')
        grid;
        
        subplot(3,2,4);
        plot(Tijd, Snelheid_kmh,'y'); hold on
        xlabel('Tijd(s)')
        ylabel('Snelheid(km/h)')
        grid;
        
        subplot(3,2,5);
        plot(Tijd,Kracht,'m'); hold on
        xlabel('Tijd(s)')
        ylabel('Kracht(N)')
        grid;
        
        subplot(3,2,6);
        plot(Tijd, Efficientie,'k'); 
        xlabel('Tijd(s)')
        ylabel('Efficientie(%)')
        grid;
        
        coefficients = polyfit(Stroom,Spanning,1);
        figure;
        scatter(Stroom,Spanning,'filled'); hold on
        Spanning_fit = Stroom*coefficients(1)+coefficients(2);
        plot(Stroom,Spanning_fit,'k');
        title('Accuspanning tegen de accustroom');
        xlabel('Accustroom(A)'); 
        ylabel('Accuspanning(V)');
        legend('Ruwe data','Benadering')
        grid;
        
        figure;
        scatter(Stroom,Spanning_fit); hold on
        Stroom = 0:5:140;
        Spanning_fit = Stroom*coefficients(1)+coefficients(2);
        plot(Stroom,Spanning_fit,'k');
        title('De fit tegen de stroom')
        xlabel('Accustroom(A)');
        ylabel('Spanning(V)');
        legend('Meetdata','Benadering')
        grid;
        
        figure;
        plot(Tijd,Spanning); hold on
        plot(Tijd,Spanning_fit,'k');

Answer 1

[Torsten]

Use

        figure;
        scatter(Stroom,Spanning_fit); hold on
        Stroom1 = 0:5:140;
        Spanning_fit = Stroom1*coefficients(1)+coefficients(2);
        plot(Stroom1,Spanning_fit,'k');
        title('De fit tegen de stroom')
        xlabel('Accustroom(A)');
        ylabel('Spanning(V)');
        legend('Meetdata','Benadering')
        grid;
        
        figure;
        plot(Tijd,Spanning); hold on
        plot(Tijd,Stroom*coefficients(1)+coefficients(2),'k');
        

instead of

        figure;
        scatter(Stroom,Spanning_fit); hold on
        Stroom = 0:5:140;
        Spanning_fit = Stroom*coefficients(1)+coefficients(2);
        plot(Stroom,Spanning_fit,'k');
        title('De fit tegen de stroom')
        xlabel('Accustroom(A)');
        ylabel('Spanning(V)');
        legend('Meetdata','Benadering')
        grid;
        
        figure;
        plot(Tijd,Spanning); hold on
        plot(Tijd,Spanning_fit,'k');

[Wouter]

That fixed a little bit of the issue, thanks.

But they main problem i have is that in this piece of code i am trying to get the two voltages i have into one graph.

I think the time (Tijd) doesn't have the same amount of points as Spanning_fit.

I probably did something completly wrong so i might just start over.

figure;
    plot(Tijd,Spanning); hold on
    plot(Tijd,Spanning_fit,'k');

[Torsten]

My code plots both graphs in the same figure.

[Wouter]

I did it wrong. Sorry man, thank you for the solution now it works!